By Ivan the Troll
Chinese researchers from the Xi’an Modern Chemistry Research Institute have found a technique that couples high explosives with SLA (resin) 3D printing to accelerate a projectile to considerable velocities…as high as 1043 m/s. This is the first instance I am aware of where 3D printing has been used to process a stand-in for propellant in a firearm-related application.
In the research paper released by the Institute (reported by 3dprintingindustry.com), they explain how they used filler resin, RDX (a high explosive), as well as a plasticizer that would give the printed parts more suitable mechanical properties. This plasticizer itself is also considered an energetic material, meaning it would explode/combust with the RDX.
Their projectile was a 200g ball (30mm bore diameter)…that’s nearly 3100 grains. At 1043 m/s (roughly 3400 fps), that’s about five times more muzzle energy than a .50 BMG round.
The most interesting thing about this test is that the Institute was able to harness a high explosive in place of a more conventional propellant (such as smokeless gunpowder). Unfortunately, their use of RDX means this isn’t some breakthrough in DIY firearms – I can’t think of many instances where you would be able to obtain RDX, but not gunpowder.
The level of muzzle energy demonstrated here is something beyond small arms, more relevant to artillery and armored fighting vehicles, at least as this point in the testing. Demonstrations of the process on a smaller scale would be interesting to see, though I imagine nobody is itching to put an RDX-powered rifle in their shoulder anytime soon.
This process has applications in future weapons system for large-scale/military applications. The advantage of being able to 3D-print the explosive/propellant cores allows the design to be custom tailored for fluid flow and ideal burn rates. This can allow for more consistency, one cartridge to the next (potential XLR or indirect fire application), and more power per case area (think +p+ artillery shells).
For more information, the research paper by the Institute is available here.